/Engine/Source/Developer/ToolMenus/Public/ToolMenu.h
Callback is passed sandboxed empty menu to add as many sections as desired. Sections merged into the final menu afterwards.
[FToolMenuSection](API\Developer\ToolMenus\FToolMenuSection) & AddDynamicSection ( const [FName](API\Runtime\Core\UObject\FName) SectionName, const [FNewSectionConstructChoice](API\Developer\ToolMenus\FNewSectionConstructChoice) & InConstruct, const [FToolMenuInsert](API\Developer\ToolMenus\FToolMenuInsert) InPosition )